Conventional combined injection-molding and pressing machines include a combination of a horizontal press and a vertical injection apparatus, and a combination of a vertical press and a horizontal injection apparatus. However, the former combination usually has such problems that the overall height of a combined machine is increased when installed, and that working efficiency is low at replacement of a screw. Therefore, the latter combination has a major widespread use in the field. For example, there is known a machine of the latter combination in which, as shown in FIG. 1 depicting a mold front view, an injection nozzle 32 is abutted or contacted with a side face 31a of a lower mold 31 on the stationary side, a hot runner 33 is machined in the lower mold 31 to extend from the contact portion thereof with the injection nozzle 32, and a heater 34 is disposed around the hot runner, for thereby injecting resin 35 into a cavity A through the hot runner (Japanese Patent Laid-Open No. 61(1986)-22917). As shown in FIG. 2 depicting a mold front view, there is also known a machine in which a hot runner is separated from a lower mold 41. Thus, a long hot runner 42 is provided to be contacted at one end with a gate of the mold 41 and at the other end with an injection nozzle 32, and heater rings 43 are disposed to cover the hot runner 42 (Japanese Patent Laid-Open No. 50(1975)-66558). These machines have made improvements in the contact point of the injection apparatus with the press and in reducing the amount of resin loss. In spite of such improvements, the conventional combined injection-molding and pressing machines constituted by combining a vertical press with a horizontal injection apparatus are still problematic. In the machine of FIG. 1, the injection apparatus is forced to extend and contract by heat. More specifically, when the injection nozzle 32 extends, the lower mold 31 is pushed to move correspondingly. When the injection nozzle 32 contracts reversely, the contact surface pressure between the injection nozzle 32 and the lower mold 31 is so reduced that the resin 35 may leak therethrough. Another problem is in that this type lower mold 31 requires the higher manufacture cost and cannot be replaced by such molds as employed in usual injection molding for common use. Still another problem is in that color changing of the resin 35 is inefficient and incomplete with the presence of the hot runner 33.
Meanwhile, in the machine of FIG. 2, as the injection nozzle 32 and the hot runner 42 extend and contract by heat, there occur shifts in the contact position between the injection nozzle 32 and the hot runner 42 and the contact position between the hot runner 42 and the lower mold 41. Another problem is that because of a long passage from the injection nozzle 32 to the lower mold 41 through the hot runner 42, color changing and purging (i.e., operation to remove dirt in the passage by running the machine while passing certain resin previously prepared at the time of color changing) of the resin are inefficient and incomplete, and quality of the products is degraded.
Furthermore, the machines of FIGS. 1 and 2 are both problematic in point of needing a large installation space. Such a problem can be coped with by providing a horizontal injection apparatus below a die plate of a vertical press. But, this arrangement gives rise to a new different problem of difficulties in replacement and/or inspection of a nozzle, a screw and the like of the injection apparatus.
In view of the state of the art as mentioned above, an object of the present invention is to provide a combined injection-molding and pressing machine with a combination of a vertical press and a horizontal injection apparatus, which is more efficient and complete in both color changing and purging of resin, which can offer an inexpensive and versatile mold that is more widely used in common, and moldings with stable quality, which can prevent a shift of the contact position between an injection nozzle and a mold even when the injection apparatus extends and contracts by heat, and which can facilitate replacement and/or inspection of a nozzle, a screw and the like of the injection apparatus.